View Full Version : A/C conversion

Sat. Nite Special
03-28-03, 10:23 PM
Hello all,

This has probably been a topic once before but......
What's everyone's opinion on converting the A/C in an '81 over to r134a?
I hear different things. From "works great" to "keeps overheating".
The old r12 has run out and it's starting to warm up outside. Gotta have the A/C soon!

03-29-03, 06:48 PM
I have heard the same stories concerning converting to 134. If you have an HVAC guy that you trust, or an appliance repair guy, there is an option to 134. Almost 3 years ago now, I had 401B installed in my 81. No parts to convert, holds approximately 3 pounds, last cost was about $15/lb. I have had no problems with overheating and it works great. 401A and 401B are used in commercial applications like trucks, and heavy equipment and is a direct replacement for R-12.

The Car Whisperer
04-20-03, 10:37 AM
I converted my 86' to R134A 3 years ago. No major problems that I can see, it is not as cold as the R12 but it is definitely cold enough. There is a booster additive that you can ad to the system charge, I have not done this yet but will probably add it this summer. Was an easy job, you do need access to some AC gauges and a vacuum pump though. Other than that it's a simple job, I bought the Interdynamics conversion kit that is sold in Wal-Mart and other auto supply stores, it has everything you need to do it other than the gauges and the vacuum pump. I borrowed a set of gauges and a pump. The kit was less than $30. If you have any leaks though forget it. From what I hear you have to have a tightly sealed sytem or you will loose the charge fast since 134a leaks out of a hole where r12 may not. I pulled a vacuum on my sytem to evacuate it and then isolated the system and checked the level of vacuum for 2 days to see if it dropped at all, it did not so I felt secure in recharging it without opening the system.

Dave L.
04-21-03, 07:40 PM
A freind of mine who works with refrigerants gave me the same story that Dale-DDL 81 related to. I am going to go with 401. I am going to have him evacuate the R12 left in the system and then I am going to replace the orifice and accumulator along with new seals on all the lines. Then have him charge it up with new oil. I hope to get to it some time this summer.


04-21-03, 08:10 PM

My A/C is still working well 2 years out. I evacuated the remaining R-12 held vacuum and checked for leaks. There was no vacuum loss so we shot 3 pounds of 401 into the system and that was it. Maintenance of seals etc. is often a good thing if want to assure yourself of no leakage in the lines. Often, in fact very often, refrigerant leakage occurs through the compressor shaft seals especially on systems that set idle for long periods of time.

Dave L.
04-21-03, 08:15 PM
Thanks Dale. I think I might just do it your way. However,he did suggest I replace the accumulator and orifice for good measure.
It looks like a major PITA to get some of those seals out!


07-14-03, 01:56 PM
What do you guys think about this conversion kit from Eckler's?


My factory air is out, it's hot, and I need to do something !!!:confused

Dave L.
07-14-03, 09:04 PM
21again - looks like a pretty good deal-accumulator,orifice,compressor all new seals... You should be good to go with that setup. Let us know what you decide and how it works out for you. And WELCOME to the Corvette Action Center!!


p.s.I still haven't got mine working yet.It looks like next year at this point!

07-15-03, 05:00 PM
FWIW, I had a friend post the 'official' GM Service Bulletin regarding conversion from R12 to R134a. Have a looksee at


More than you probably want to know, but......

Hope it helps...


07-19-03, 09:55 AM
I've used 414B as a drop-in replacement (with no oil changes) for R-12 for almost ten years now, with no problems. It performs bertter than either R-12 or R134A, and better than many other tertiary blends. "Better" meens more latenet heat capacity (improved cooling) and at lower operating pressures. The operating pressures are something worth considering on refrigeration equipment that is 20+ years old, like in your car. Since R134A operates at significantly higher pressures at a given temperature, the strain on your older system components may not be desirable.

07-19-03, 03:13 PM
Another concern that you haven't addressed is that substitute refrigerants that drop evaporator temps lower than R12 can cause core freeze problems.

Most of these systems prevent this with a low pressure cycling switch. When the compressor pulls the suction side down to about 20 psi, it disengages the compressor. Once the pressure rises to about 40-45 psi, it kicks it back in. Most systems limit core temps to 35-38 deg to prevent this. The switch pressure is determined to correlate to that temp.

If there is a significant difference in the refrigerant temperature at the switch off pressure, the evaporator temps can be pulled below 32 F and freeze the water in the air stream. This can result in evaporator leaks and corrosion problems, especially in older equipment.

Glad to heasr you haven't had problems, but this occurs all too often with these "more efficient" substitutes for R12.


07-19-03, 09:14 PM
401B is nearly identicle to R-12, and is "drop in" as you say with out any orifice change or oil change. Mine has been in 3 years now with no problem what so ever. Total cost to evacuate and re-fill with 3 pounds of 401B $78.